Center for dividers.



No. 841,713. PATENTED JAN. 22, 1907. GLE. PERRY.

CENTER FOR DIVIDBRS. APPLICATION FILED AUG. 26.1905.

FIG. 2.

INVE'NTOR:

WITNESSES;

- By AZ/OIIZEJUZI.

UNITED STATES PATENT OFFICE.

CENTER FOR DIVIDERS.

Specification of Letters Patent.

Patented Jan. 22, 1907.

Application filed August 26, 1905. Serial No. 275,888.

To (1,7 2 1071,0171, it may concern:

Be it known that I, GEORGE ELLIOT PERRY, a citizen of the United States, residing in Jersey City, in the county of Hudson and State of New Jersey, have invented cer tain new and useful Improvements in Centers for Dividers, of which the following is a specification.

My invention aims to provide an improved point or center for dividers, compasses, or other tools which are used to strike an are or which swing about a fixed point. Such centers are usually steel pins having a continuous tapering point or having a fine needlepoint at the center surrounded by a flat horizontal shoulder. Even with the latter type of centers, which are designed especially for fine work, it is found that the needle-point must be of considerable size at its base in order to have sufiicient strength, and as the entire point or needle enters the paper it makes a hole of the size of the base, which is so large as to be disadvantageous in most accurate work, especially where a number of arcs have to be struck from the same center. The construction is such also as to permit a certain minute amount of play of the needlepoint in the hole, which enlarges the hole after it has been used a number of times. The present invention aims to provide a center which shall make the smallest possible hole in the paper and which shall have little or no lateral play in the hole, thus insuring a small and accurate hole even after it has been used as the center of a number of arcs in succession. To this end a needle is formed with an adjacent downwardly-extending bearing point or edge slightly above the point of the needle, which edge is at a fixed distance above the point, and thus limits the penetration of the needle into the paper and at the same time itself penetrates the paper sufficiently to assist the needle in preventing lateral play of the center. The improved center at the same time costs no more than centers of the type already in use.

The accompanying drawings illustrate an embodiment of the invention.

Figure 1 is an elevation of a pair of dividers with the center in place. Fig. 2 is a vertical diametral section on an enlarged scales Fig. 3 shows the impression made upon the paper by the center when in use.

Referring to the embodiment illustrated, A indicates as a whole the center, which is ordinarily adjustable in the leg B of the dividers. The center is formed in the present case with a needle C and an adjacent downwardlyextending edge D, the edge D being preferably circular and integrally or otherwise fixedly attached to the needle, with the needle C at the center of the circle. The device may be conveniently formed in a single integral piece by turning the end in a watchmakers lathe to form a concave shoulder E around the needle. By this construction the needle is provided with a wide base F, so as to give it strength, while the portion which enters the paper is nevertheless of very minute diameter, so as to make the smallest possible hole in the paper. The paper is represented at G, and it will be observed that the edge D of the center serves as a stop to limit the penetration of the needle C, so that the hole made by the needle will only be as large as the diameter of the needle at approximately the level of the edge D. Thus a needle of sufficient strength and a hole in the paper of minimum diameter are secured. The edge D of the center also tends to prevent lateral movement, either by its friction on the paper or board G or by itself penetrating slightly into such paper to form a ring H, Fig. 3, thus permitting of the use of the same hole a number of times without increasing its size. With ordinary pressure the ring H is almost or quite imperceptible; but by exerting a sufiicient pressure the ring is made more prominent and serves to mark the position of the central hole, a point of considerable value with the very minute hole made by the needle.

It is to be understood that the center is not necessarily a movable pin, such as is shown. It may be used in various other instruments besides the dividers illustrated and may be manufactured in other ways than that described. The adjacent bearing is not neces sarily a complete circular edge, but may be any part of a circle, however small. For example, it may be a flat plate of the contour of Fig. 2. The needle may be a separate piece of metal from the adjacent shouldered part.

By reason of the protection against lateral strain on the needle the needle may be made of harder and less springy metal than is customary for ordinary centers with fiat shoulders, thus making a center which preserves the sharpness of its point longer than usual.

which is adapted to limit the penetration of the needle to a distance less than its full length and at the same time to tion of the needle.

2. A center for dividers, having a needle C at the base of which is a concave shoulder E forming a surrounding edge D above the point of the needle, the whole being made of :20 a single integral piece of metal.

In witness whereof I have hereunto signed my name in the presence of two subscribing Witnesses.

GEORGE ELLIOT PERRY. Witnesses:

DOMINGO A. UsINA, THEODORE T. SNELL.

permit rota- 15 

